1076 The American Naturalist. [December. 
Other branches of zoology show similar variations. Dr. Car- 
penter, speaking of the Foraminifera, says in the Introduction 
(quoted by Wallace in " Natural Selection," pp. 162, 163) that an 
immense number of specimens of different species had passed 
under the observation of himself and Messrs. Williamson, Parker 
and Rupert Jones, and the result of the observation is said to be 
that " the range of variation is so great among the Foraminifera 
as to include not merely those differential characters which have 
been usually accounted specific, but also those upon which the 
greater part of the genera, and even in some instances those of 
its orders" are founded. 
Mr. Wallace also refers (p. 165) to the studies of Bates upon 
butterflies, stating that " during eleven years he accumulated 
vast materials, and carefully studied the variation and distribution 
of insects. Yet he has shown that many species of Lepidoptora, 
which before offered no special difficulties, are in reality most 
inextricably combined in a tangled web of affinities, leading by 
such gradual steps from the slightest and least stable variations, 
to fixed races and well-marked species, that it is very often 
impossible to draw those sharp dividing lines which it is supposed 
that a careful study and full materials will always enable us to do." 
Swainson, writing in 1835, in his volume "On the Geography 
and Classification of Animals," in speaking of the features which 
characterize species (p. 277), says that in some genera of the 
Dynastidae the horn-like protuberances which distinguish the 
male sex vary in their length in almost every individual, — so 
that in some they are very prominent, while in others they are 
more like short tubercles." And again he says : " The spines 
upon the different rock-shells (Murex), and on the coronated 
volutes (Cymbiola, Sev.), vary in like manner,— some specimens 
having acute and prominent spines,while others are nearly smooth. 
In still another group of animals, the sponges, great confusion 
exists. Prof Alexander Agassiz ( " Three Cruises of the Blake," 
Vol. II., p. 1 70) says that here "all our ordinar>' notions of indi- 
viduality of colonies, or of species, are completely upset. It 
seems as if in the sponges we had a mass in which the different 
parts might be considered as organs capable in themselves of a 
